(1) Field of the Invention
This invention relates to a retractor for controlling the winding and release of a webbing in a seat belt system for restraining an occupant in a seat of a vehicle such as automobile, and more specifically to a retractor permitting a forcible release of a webbing from a locked state in the event of an emergency such as over-turn of a vehicle.
(2) Description of the Prior Art
A retractor suitable for use, e.g., in a so-called passive belt system which does not include any buckle has been conventionally constructed in such a way that an associated webbing can be forcibly released from its locked state, because if the webbing remains in its locked state in the event of an emergency such as over-turn of a vehicle, the occupant is held continuously in the seat and cannot evacuate the vehicle immediately when the fuel of the vehicle has caught fire, and this is certainly dangerous. On the other hand, it is also important that the occupant can be restrained in the seat to avoid collision against the front glass when the vehicle is stopped abruptly and can also be held surely in the seat to prevent him from being thrown out from the vehicle when the vehicle rolls over. It is hence required to construct the retractor in such a way that the webbing is held surely in a locked state to hold the occupant in the seat in the even of an emergency.
When the vehicle has rolled over on the other hand, it is critical that the occupant is allowed to evacuate the vehicle as quickly as possible. For this purpose, it is also necessary to construct the retractor in such a way that the occupant can easily and surely release the webbing from its locked state. This requirement is contradictory with the above-mentioned requirement that the webbing should be locked as quickly as possible. Although a variety of retractors which permit a forcible release of a locked state have been proposed to date, none of such conventional retractors is believed to satisfy these contradictory requirements fully and many of them are suspicious in their sureness in operation with respect to forcible release of their locked states.